1. Field
Embodiments of the invention relate to cannulas and trocars and, in particular, to devices, systems, and methods for adjusting opening sizes of cannulas.
2. Description of the Related Art
Cannulas typically are tubes inserted into a body part for allowing insertion of fluids, materials, or instruments through the cannula or to allow the drainage or removal of fluids.
The smaller in cross-section that a cannula is, the less trauma is caused to the tissue surrounding the cannula. Recent developments in ophthalmology provide a good example of the benefits of small diameter cannulas. It has become increasingly common for vitreoretinal surgery to use cannulas sized small enough to pass instruments of 23 gauge (ga.) or less through the cannula. This then allows the incision from the cannula site to be small enough to self-seal without having to use sutures. This self-sealing of the incision in-turn allows the cannula to be inserted transconjunctivally, saving time and eliminating the need to incise and retract the conjunctiva before incising the sclera, as required using 20 ga. or larger instruments. While the use of smaller sized cannulas has been beneficial, the necessity of using smaller sized instruments has reduced the efficiency of some aspects of surgery compared to the older standard of using 20 ga. instruments. For example, the use of a vitreous cutter with a 23 ga. or smaller outer diameter takes more time to remove vitreous compared to a 20 ga. outer diameter cutter. Also, the insertion of viscoelastic material through a 23 ga. or smaller lumen is more difficult and time consuming compared to using a 20 ga. lumen. Therefore, it would be desirable to have a cannula system that provides the small incision advantages of a self-sealing incision while still allowing the use of more efficient larger diameter instruments.
Certain aspects, advantages, and novel features of the invention are described in this disclosure. It should be understood that not all possible aspects, advantages, and features may be employed or achieved in accordance with any particular embodiment of the invention.